Removing duplicated descriptions

Removed dupliocated Mistral overviews and merged content into description on
 index page.

Change-Id: Ia7c260494a8a659988db2329bf3504be9b4b67fa
Signed-off-by: Andrea Visnyei <andrea.visnyei@nokia.com>

doc/source/admin/architecture.rst

@@ -2,10 +2,6 @@
 Mistral Architecture
 ====================
 
-Mistral is OpenStack workflow service. The main aim of the project is to provide
-capability to define, execute and manage tasks and workflows without writing
-code.
-
 
 Basic concepts
 ~~~~~~~~~~~~~~

doc/source/admin/install/get_started.rst

@@ -2,14 +2,6 @@
 Workflow Service Overview
 =========================
 
-Mistral is a workflow service that enables setting up and scheduling tasks and
-task relations that have to be executed in a particular order, called workflows.
-During execution, Mistral handles state management, correct execution order,
-parallelism, synchronization and high availability.
-
-Mistral can be used, for example, for Cloud Cron-style task scheduling,
-Cloud Environment Deployment, handling long-running business processes, managing
-BigData analysis and tasks, and live migration.
 
 The Workflow service consists of the following components:
 

doc/source/index.rst

@@ -5,9 +5,26 @@ Mistral Workflow Service
 What is Mistral?
 ================
 
-Mistral is a workflow service project. It aims to provide a mechanism
+Mistral is a workflow service. Lots of computations in computer systems
-to define complex graphs of tasks (workflows) in a simple YAML-based
+nowadays can be represented as processes that consist of multiple
-language and manage and run them in a scalable and reliable manner.
+interconnected steps that need to run in a particular order. Those steps
+are often interactions with components distributed across different machines:
+real hardware machines, cloud virtual machines or containers. Mistral provides
+capabilities to automate such processes.
+
+Particularly, Mistral can be used, for example, for solving administrator
+tasks related to managing clusters of software, or for any other tasks
+that span multiple components and take long to complete. It can also be used
+as a central component for deploying distributed software in a truly large
+scale. In any case where the ability to track the progress of the activity
+becomes crucial, Mistral is a good fit.
+
+A Mistral user can describe such a process as a set of tasks and transitions
+between them, and upload such a definition to Mistral, which will take care of
+state management, correct execution order, parallelism, synchronization and
+high availability. In Mistral terminology such a set of tasks and
+relations between them is called a **workflow**.
+
 
 Just to Get Started
 ===================

doc/source/user/overview.rst

@@ -1,20 +1,6 @@
 Quick Overview
 ==============
 
-What is Mistral?
-----------------
-
-Mistral is a workflow service. Most business processes consist of multiple
-distinct interconnected steps that need to be executed in a particular order
-in a distributed environment. A user can describe such a process as a set of
-tasks and their transitions. After that, it is possible to upload such a
-description to Mistral, which will take care of state management, correct
-execution order, parallelism, synchronization and high availability. Mistral
-also provides flexible task scheduling so that it can run a process according
-to a specified schedule (for example, every Sunday at 4.00pm) instead of
-running it immediately. In Mistral terminology such a set of tasks and
-relations between them is called a **workflow**.
-
 Main use cases
 --------------